Seems like pretty straight forward setup, 8 zone controller should work for you.

You may have trouble connecting all four of your common wires to a single C terminal on 8 port Rachio, I recommend you split them into two pairs and twist the ends of each pair together before inserting them into separate C terminals (you will have 2 of the C terminals on 8 zone version).

Alternately get a cheap wire nut from your local home depot or lowes and twist all of the commons together with a new wire going from newly made bundle to one of the C terminals of your new Rachio. This will allow you to leave a second one available just in case.

@the_paper_pusher - @Gene is right on with the wire nut option to leave an open common port for you. Other than checking to see that you have WiFi signal at that location (at least non-weak) and power to plug in the Rachio, you should be good to go. The wiring is straight forward. If/when you have any questions on zone settings post back to the board and I’m sure someone will jump in an assist.